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Abstract:

This invention relates to metallic towers or the like utilized for
electric power transmission lines, telecommunications, wind energy
generators and other applications. The standard sections used in lattice
towers of the prior art have structural and aerodynamic deficiencies. To
overcome the drawbacks and problems the prior art one aspect of the
present invention is directed to a metallic tower comprising lattice
members with a channel section, wherein the length of the channel web is
smaller than the length of the channel legs.

Claims:

01. A metallic tower characterized by comprising lattice members with a
channel section, wherein the length of the channel web is smaller than
the length of the channel legs.

02. A metallic tower according to claim 01, wherein the channel section
with reduced web has equal gyration radius in all axes.

03. A metallic tower according to claim 01, wherein the lattice members
with the channel section with reduced web are the bracing diagonal
members.

04. A metallic tower according to claim 01, wherein the lattice members
with the channel section with reduced web are the horizontal bars.

05. A metallic tower according to claim 01, 02, 03 or 04, wherein the
lattice members with channel section with reduced web are positioned in
the tower with minimum area facing the wind.

06. A metallic tower according to claim 01, 02, 03 or 04, wherein channel
section with reduced web has an optimized aerodynamic profile.

07. A metallic tower according to claim 01, 02, 03 or 04, the channel
section with reduced web has rounded edges.

08. A metallic tower according to claim 01, 02, 03 or 04, wherein the
channel section with reduced web has stiffener elements.

09. A metallic tower according to claim 01, 02, 03 or 04, wherein the
channel section with reduced web is covered by a cowling with an
optimized aerodynamic profile.

Description:

TECHNICAL FIELD

[0001] This invention relates to metallic towers or the like utilized for
electric power transmission lines, telecommunications, wind energy
generators and other applications.

BACKGROUND ART

[0002] Towers or the like utilized for electric power transmission lines,
telecommunications, wind energy generators and other applications are
well know in the prior art. The structural designs, components and
materials of such towers vary depending upon the application.
Nevertheless, due to structural design and cost constraints, it is very
common the use metallic lattice towers in high voltage electric power
transmission and telecommunications applications.

[0003] In such lattice towers, the skilled in the art usually adopt the
standard sections such as the ones described in the European Standard
prEN 1993-3-1:2004--Eurocode 3: Design of steel structures, Part 3.1.:
Towers, masts and chimneys--Towers and masts.

DISCLOSURE OF INVENTION

Technical Problem

[0004] The standard plane sections usually have different values for the
radius of gyration according to the symmetry axis of each section. The
critical load for dimensioning the truss members is the buckling load
under axial compressive stress. As truss members are structurally
slender, the critical load is inversely proportional to the square of the
gyration radius where it is adopted the minimum gyration radius of the
section, the utilization of the greater strength in the other axes is
hindered. In addition, the standard sections with plane faces, besides
having different radius of gyration in each axis, have sharp edges and
were not conceived for reducing the aerodynamic forces on the towers.

Technical Solution

[0005] To overcome the drawbacks and problems described above and other
disadvantages not mentioned herein, in accordance with the purposes of
the invention, as embodied and broadly described herein, one aspect of
the present invention is directed to a metallic tower comprising lattice
members with a channel section, wherein the length of the channel web is
smaller than the length of the channel legs.

[0006] In accordance with one aspect of the invention, the channel section
with reduced web has equal gyration radius in all axes.

[0007] In accordance with one aspect of the invention, the lattice members
with the channel section with reduced web are the bracing diagonal
members.

[0008] In accordance with one aspect of the invention, the lattice members
with the channel section with reduced web are the horizontal bars.

[0009] In accordance with another aspect of the invention, the lattice
members with the channel section with reduced web are positioned in the
tower with minimum area facing the wind.

[0010] In accordance with another aspect of the invention, channel section
with reduced web has a more aerodynamic profile, and with less area
facing the wind.

[0011] In accordance with another aspect of the invention, the channel
section with reduced web has rounded edges.

[0012] In accordance with another aspect of the invention, the channel
section with reduced web has stiffener elements.

[0013] In accordance with another aspect of the invention, the channel
section with reduced web is covered by a cowling with an optimized
aerodynamic profile.

Advantageous Effects

[0014] The present invention has several advantages over the prior art. By
adopting truss members with reduced channel section with reduced web, it
is obtained optimized gyration radius in all axis directions, reduced
section area facing the wind and lower drag coefficients. Therefore, due
to the improvement in the aerodynamic and structural performance and
behavior it is obtained a surprising reduction in the total weight of the
structure, beside the reduction of the loads over the basement. This
surprising effects are obtained even using the same silhouette of a prior
art truss tower. Consequently, even for the same silhouette, a
significantly more economical tower is obtained. Nevertheless, with the
re-adequation of the silhouette design to the new aerodynamic and
structural forces, the advantages of the present invention become even
more significant. Moreover, the possibility of unrolling the metal sheets
in automated machines for cutting, bending and perforating, allows
significant manufacturing productivity gains, including the elimination
of scrap.

DESCRIPTION OF DRAWINGS

[0015] The accompanying drawings are not necessarily drawn on scale. In
the drawings, each identical or nearly identical component that is
illustrated in various figures is represented by a like numeral. For
purposes of clarity, not every component may be labelled in every
drawing.

[0016]FIG. 01 is an extraction of the `FIG. 1.1.` of the European
Standard prEN 1993-3-1:2004.

[0017]FIG. 02 illustrates one exemplary embodiment of a channel section
according to the invention.

[0018]FIG. 03 illustrates one exemplary embodiment of a channel section
and a cowling according to the invention.

[0019] FIG. 04 illustrates a perspective view of an exemplary embodiment
of a section of a triangular tower module according to the invention.

[0020]FIG. 05 illustrates a frontal view of an exemplary silhouette of a
triangular tower.

[0021]FIG. 06 is an enlarged view of the detail `A` of FIG. 05,
illustrating one module of the tower.

[0036] This invention is not limited in its application to the details of
construction and the arrangement of components set forth in the following
description or illustrated in the drawings. The invention is capable of
other embodiments and of being practiced or of being carried out in
various ways. Also, the phraseology and terminology used herein is for
the purpose of description and should not be regarded as limiting. The
use of `including`, `comprising`, `having`, `containing` or `involving`,
and variations thereof herein, is meant to encompass the items listed
thereafter and equivalents thereof as well as additional items.

[0037]FIG. 01 is an extraction of the `FIG. 1.1.` of the European
Standard prEN 1993-3-1:2004--European Standard prEN
1993-3-1:2004--Eurocode 3: Design of steel structures, Part 3.1.: Towers,
masts and chimneys--Towers and masts, which shows the `Dimensions and
axes of sections`, including `Commonly used sections` and `Other
sections`. Such common standard sections are well described in other
handbooks and standards, and are usually adopted by the skilled in the
art when designing truss towers.

[0038]FIG. 02 illustrates one exemplary embodiment of the channel (1)
section (also denominated as U-Section`) with a reduced web (2) according
the present invention. As shown, the length (B) of the channel (1) web
(2) is smaller than the length (L) of the channel (1) legs (3), which
therefore for the sake of simplicity, may be denominated as a `channel
section with reduced web`. In this example, the gyration axis is the same
in all axes.

[0039] As shown in the example of FIG. 02, the reduced web (2) of the
channel (1) section has rounded edges. In accordance with another aspect
of the invention, channel (1) section with reduced web (2) has an
aerodynamic profile.

[0040] In accordance with another aspect of the invention, the channel
section with reduced web can have stiffener elements, which may be
intermediary or in the edges.

[0041]FIG. 03 illustrates one additional embodiment of the invention,
wherein the channel section with reduced web is covered by a cowling (1a)
with an oblong aerodynamic profile, which is the best for this case. The
function of the cowling is to cover the channel section as an involucre,
enhancing the aerodynamic of the metallic section with a low cost
material an easy formation, such as polymers, composite materials or
other materials.

[0042] FIG. 04 illustrates a perspective view of a part of an exemplary
section of a triangular tower module, with tubular columns (4). In this
example, the truss members with channel (1) section with reduced web (2)
are the bracing diagonal members.

[0043]FIG. 05 illustrates a frontal view (elevation) of an exemplary
silhouette of a triangular tower. The skilled in the art usually adopt
for the bracing diagonal (5) members and horizontal bars (6) the
`Commonly used sections` and `Other sections` as mentioned in FIG. 01. By
the contrast, in the exemplary embodiment of the module shown in FIG. 06
of the triangular tower of FIG. 05 and respective enlarged details shown
from FIG. 06 through FIG. 10, the bracing diagonal (5) members are
channel (1) sections with reduced webs (2). In accordance with one aspect
of the invention, the lattice members with the channel (1) section with
reduced web (2) can be horizontal bars (6).

[0044] Based in this disclosure, many possibilities of design may be
apparent for a skilled in the art, such as combining reduced web (2)
bracing diagonal (5) members with reduced web (2) horizontal bars (6); as
well combining reduced web (2) channel (1) sections with prior art
standard sections. All such combinations are also intended to be
encompassed by the invention and following claims.

[0045] Other modifications in the details of construction may be possible.
For instance, the bolts and nuts connections shown in the enlarged views
of FIGS. 06 through FIG. 10 may be substituted by welded joints, groove
coupling or any other suitable connection means. Another example of
possible substitution would be the top flange shown in FIG. 05, which may
be substituted by a slip-joint connection system, for instance. The
vertical columns (tower support leg members) may be of any other adequate
section for each case. The quantity and displacement of the vertical
columns may vary, being more common three columns forming an equilateral
triangle or four columns in quadrangular format. Other variations in the
components and project may be possible according the application.

[0046] For illustrative purposes and non-limiting, in the Table 1 there
are shown the characteristics of a channel section with reduced web,
identified as "U", according to one ex-emplificative embodiment of the
invention, compared to a angle section with equal legs, identified as
"L", usually adopted in the prior art.

[0047] In this example, the sections were projected to support the same 21
kN axial compression load, with distance between rotulas of L=1.5 m. For
the sake o simplicity, it was adopted buckling stress given by the
equation T=10.4×106/ Y2 for Y>86 where Y=L/i and
L=distance between rotulas and i=gyration radius.

[0048] The Table 1 shows three very important aspects: a) the strength of
the channel section with reduced web is 3% greater than the `L` angle
section; b) the weight of the channel section with reduced web is 33%
lower than the weight of the `L` angle section; and c) the wind load over
the channel section with reduced web is 41% lower than the `L` angle
section. The synergy due to these three factors: substantial maintenance
of the strength, or even increase of the strength; reduction of the dead
weight of the section; and reduction of the wind loads over the
structure, provide a surprising improvement in the performance of the
entire structure, with the possibility of increasing the self-frequency
of the tower and reducing the costs of the tower and of the basement.

[0049] For illustrative and exemplificative purposes, not limiting the
present invention, FIGS. 11 a 20 shows the dimensioning spreadsheets and
label of three 70 meters high self-supporting triangular towers, with the
same silhouette the exemplar tower of FIG. 04, with frusto-conical
columns with three modes of trusses for the same loads.

[0050] In the Tables II.1-3, FIGS. 11 to 13, the truss members used are
angle sections with equal legs according the prior art. The total weight
of the tower would result in 13.558 kg (133 kN). In the Tables III.1-3,
FIGS. 14 to 16, the truss members, diagonal braces and horizontal bars,
used are channel sections with reduced web. The total weight of the tower
would result in 10.746 kg (105 kN). In the Tables III.1-3, FIGS. 17 to
19, the truss members, diagonal braces and horizontal bars, used are
channel sections with reduced web with aerodynamic cowlings according
FIG. 03. The total weight of the tower would result in 9.707 kg (95.2
kN).

[0051] Therefore, due to the improvement in the aerodynamic and structural
performance and behavior it is obtained a surprising reduction in the
total weight of the structure, beside the reduction of the loads over the
basement. This surprising effects are obtained even using the same
silhouette of a prior art truss tower. Consequently, even for the same
silhouette, a significantly more economical tower is obtained.

[0052] While the invention has been disclosed by this specification,
including its accompanying drawings and examples, various equivalents,
modifications and improvements will be apparent to the person skilled in
the art. Such equivalents, modifications and improvements are also
intended to be encompassed by the following claims.